Adsense has one small info button on the top right where you can click and report, however, for Youtube video ads, there's no visible way to report them as well, especially softcore porn. What's worse is that Youtube doesn't care whether the current audience is suitable or not as long as the ads were shown at the intended target ( ie gaming related video )

I had to do that because of the sheer amount of softcore porn (ads for Chinese livestream services such as MeMe and MoreIn) in the YouTube adverts in my region.

Google was showing softcore porn images and words on kids videos in Dutch recently, and I couldn't figure out any way to send a note about the ads (just say that they weren't relevant to me).